Just wanted to share my recipe for getting four haywire blasters out of one box of Scourge! I've seen the topic discussed before but I haven't seen this mentioned. Inspired pretty heavily by a post on dakkadakka about using the wych punch-dagger.
Basically, I used the sheathed knives in the scourge box as ornate HWB prongs. Cut the handles off, and file so there's a flat edge on the inside of the curve, next to where the handle was.
Then they just glue neatly onto the end of the heat lance. The splinter cannon and dark lance just need the end of the barrel shaping and un-adorning, and you can do the same to them. You end up with some really decorative, similar looking weapons that look like tridents, and have a bit of individuality which is how I think Scourges would probably roll.
I always imagined that the prongs at the end of the HWB open up when it's fired, something like the overcharged plasma pistol from Halo, and that's just what these look like when they're done. I actually think my real HWB looks pretty boring in comparison, but you don't get enough knives to do it to that one as well.
Once I have a device capable of such a feat, I'll take some photos (and put a million updates on my plog!) but for now, hope you can dig the idea on a no-bitz-budget.